There are some potential problems with the use of lay testimony. One is that lay testimony is always subject to interpretation. Lay witnesses are testifying about personal sensory experiences (Nordberg, 2007). All such experiences are interpretative to some extent. Another potential problem with the use of lay testimony is that it may not be interpreted as credible relative to expert testimony. Clearly in the Dube case it was, but this is a substantial risk for a legal team to take. Expert witnesses have credibility that stems from advanced training and perceived objectivity. Lay witnesses can merely interpret their own experiences. This brings us to another weakness of lay testimony -- it can only reflect personal experience. Whereas experts do not need to have direct involvement in the case events, lay witnesses do. They are therefore unable to comment on anything other than what they saw directly. The prosecution in the Dube case relied on witnesses to the crime, but had the defense entered substantial evidence of insanity outside of the actual robbery, the prosecution would have required more than just lay testimony to refute it.

The final holding of the case is that the conviction stood and the appeal was rejected. The significance of this case to lay testimony is that the judge allowed the lay testimony to essentially...

The weight and credibility of both the expert and lay testimony was given weight by the jury. This case showed that if the expert testimony is sufficiently weak, it can be overruled by a jury. The standard is that a reasonable man has to have reason to doubt Dube's sanity in order to acquit. In this instance, the expert testimony was deemed insufficient as to cause such doubt. One of the main weaknesses in this case is that some of the events upon which the expert testimony (diagnosis) was based were specifically refuted by the lay witnesses. Thus, the prosecution was able to demonstrate to the jury that the expert witnesses were not particularly credible and that greater weight should be given to the lay testimony. The lay testimony gave the jury reasonable doubt as to the testimony of the expert witnesses. With the testimony of the expert witnesses discounted, there was insufficient other evidence presented to the jury to cause a reasonable doubt of sanity.
Works Cited:

United States of America v. Roland William Dube. Retrieved April 7, 2009 from http://bulk.resource.org/courts.gov/c/F2/520/520.F2d.250.75-1034.html

Nordberg, Peter. (2007). The Daubert Worldview. Daubert. Retrieved April 7, 2009 from http://www.daubertontheweb.com/Chapter_1.htm